A myb transcription factor designated MTF is disclosed that negatively regulates plant transformation susceptibility. An integrin domain-like protein (which is under negative regulation by MTF) is involved in Agrobacterium attachment to plant cells and, thus, is a positive mediator of transformation: plants over-expressing the integrin domain-like protein are more susceptible to transformation, whereas plants mutant for the integrin domain-like protein are less susceptible. Manipulation of these elements allows improved control of Agrobacterial transformation of plants, including in crops.
Agrobacterium-mediated plant transformation forms the basis for the modern agricultural biotechnology industry.
Agrobacterium tumefaciens causes the disease crown gall and genetically transforms numerous plant, fungal and animal species. Virulent Agrobacteria harbor a tumor-inducing (Ti) plasmid containing virulence (vir) genes required by the pathogen for transport of transferred (T-) DNA and virulence effector proteins to host cells. Induction of vir genes, processing of T-DNA from the Ti-plasmid, attachment of the bacteria to plants, and subsequent transfer of T-DNA and Vir proteins to host cells are complex processes. Numerous studies have elucidated the events governing these processes in the bacterium, but relatively little is known about the plant contribution to transformation.
Although Agrobacterium has a broad host range, many economically important plants remain recalcitrant to transformation. Scientists have used a variety of techniques to identify plant genes that are involved in Agrobacterium-mediated transformation. Among these, forward and reverse genetic screens revealed more than 125 Arabidopsis and tobacco genes involved in transformation. Collectively these lines, designated “rat” (resistant to Agrobacterium transformation), reflected their attenuated response to transformation. The genes identified represent steps necessary for successful transformation, including bacterial attachment/biofilm formation, T-DNA and Vir protein transfer, cytoplasmic trafficking and nuclear targeting of the Vir protein/T-DNA complex (T-complex), Vir protein removal, T-DNA integration, and transgene expression. However, none of these mutants identify genes globally affecting plant transformation susceptibility.